The present invention relates to a method according to the preamble of claim 1.
The invention also relates to a device according to the preamble of claim 6.
A level measuring system working with radar for a tanker""s load tanks is previously known from U.S. Pat. No. 4,665,403. In load tanks of this kind, however, at least one overfill alarm independent of the level measuring system is required. The requirement for independence means that there must not be common electrical circuits and cabling, i.e. there must not be any galvanic contact between different measuring systems. However, fixed mechanical constructions for example, which cannot normally go wrong, may be shared. Float sensors and different types of capacitive sensors, for example, mounted in separate tank bushings are used as sensors for such alarm systems. These sensors are however sensitive to linings, corrosion and other influence from the content of the load tanks or their wiring and the risk of malfunction is therefore evident.
The object of the present invention is to achieve a method of the type indicated by way of introduction which is not marred by the disadvantages described above. This object is achieved by the features stated in claim 1.
The invention also has the object of producing a device according to claim 6 which is improved compared with the prior art. This is achieved with the characterizing features stated in said claim.
A number of other advantages are obtained with the invention. By utilizing a single aerial for two or more level measuring channels, costs are saved for further aerials and fitting in the tank as well as the tank bushing for these. If two measuring channels are identical, redundant measuring results are obtained, which if they only lie within a certain tolerance range are proof that the measuring channels are functioning. Several identical measuring channels also make the stocking of spare parts easier and cheaper.